1. Field of the Invention
The present invention relates to a pressurized medium cylinder having an inner chamber and a piston arranged for a reciprocable motion in the inner chamber; a longitudinal slot extending over the complete length of the cylinder; a steel strip located at the inner side of the cylinder and sealing the longitudinal slot, which steel strip extends at the area of the piston through same.
Pistons of this kind, which are also termed as piston rod-less pressurized medium cylinders, are generally known. The steel strip which is located at the inner side is arrested, for instance by means of magnets.
2. Description of the Prior Art
A pressurized medium cylinder has been disclosed in the German specification DE-PS 28 33 533, of which the inner chamber having substantially the shape of a circular cylinder is flattened at both sides of the longitudinal slot, such that the steel strip bends to a lesser extent. The steel strip is chamfered at its inner side in the area of its longitudinal edges.
A further pressurized medium cylinder of the kind referred to above is disclosed in the publication WO 83/02306, at which arresting members for a clamping into the side walls of the longitudinal slot are arranged at the side of the sealing strip of steel facing outwards. Such arresting member may be, for instance, a continuous profiled member of a plastic material having a U-shaped cross section, of which the legs are prestressed outwardly or such can be pairs of individual metal clamps. The object of these arresting members is to arrest the steel strip at the area of the slot such that magnets are no longer needed.
According to, furthermore, the specification EP-B1-69199 it is also known to place a plastic strip at the inner side and a further plastic strip at the outside of the tube, which two strips are arrested or held, respectively, at each other in a zipper-like fashion in such a manner, that the inner sealing strip is fixedly held by an outer sealing strip.
Further pressurized medium cylinders of the kind referred to above are disclosed in the European Patent Publications EP-A-260344 and EP-A-147803 and the British Patent Publication GB-A-2163499.
Due to their longer useful lifetime sealing strips made of steel are preferred.
A problem encountered at long cylinders is that the sealing strip can move laterally, i.e. orthogonally to the longitudinal extent of the cylinder. This moving cannot be prevented by the magnets because their force acts substantially in a radial direction relative to the cylinder.